maths/logic puzzle!

 

I borrowed 100 roubles from you.  Then I went shopping and lost that money.  But then I met my friend and borrowed 50 roubles from her.  I was able to buy two chocolate bars costing 10 roubles each, leaving me 30 roubles.  I repaid part of my debt to you with that 30 roubles, making me owe you further 70 roubles, as well as 50 roubles to my friend.  In all, 120 roubles.  Plus I have two chocolate bars.

 

Total: 140 roubles.  I am 10 roubles short!  Where are they?

 

 

PS rouble is russian currency, for those who didn't know.

 

Edit: have the answer:

 

Think about it. The 50 roubles borrowed from the friend doesn't get lost anywhere. Imagine you didn't buy any chocolate bars, you just gave back 30/50 roubles. That leaves you with 20 roubles, with your total debt being 120 roubles. You own 20 roubles, and you owe 120, so if you wanted to you could repay more of your debt with the remaining 20 roubles and get your debt down to 100 roubles. This 100 roubles is the money which you initially borrowed (and proceeded to lose).

Edited February 12, 201610 yr by Apaec

brb changing my answer

Edited February 12, 201610 yr by Botre

You removed 10 roubles by replacing the 30 roubles you paid with chocolate bars worth 20.

By repaying the 100, the question just becomes more confusing. Lets try to explain this.

 

Debt:

100

50

 

You spend 20, and you got 30 + 2 chocolates left.

 

 

 

You repay 30.

 

Debt:

 

100

20

 

You're now 120 in debt + the chocolate you got yourself. Which adds up. Sell the chocolate for 20, and repay 20. You're now 100 in debt.

 

 

You're mixing what you have and what you owe. 

 

TL:DR: Don't do 120 + 20 = 140. Do 120 - 20 = 100. Calculate how much you owe.

 

Edited February 12, 201610 yr by Shudsy

Because you are adding what you have to what you owe.

• +100
• +50
• -30
• you owe 120 (so -120)

By repaying the 100, the question just becomes more confusing. Lets try to explain this.

 

Debt:

100

50

 

You spend 20, and you got 30 + 2 chocolates left.

 

 

 

You repay 30.

 

Debt:

 

100

20

 

You're now 120 in debt + the chocolate you got yourself. Which adds up. Sell the chocolate for 20, and repay 20. You're now 100 in debt.

 

 

You're mixing what you have and what you owe. 

 

TL:DR: Don't do 120 + 20 = 140. Do 120 - 20 = 100. Calculate how much you owe.

 

 

you nailed it ! well done

The formula to calculate the total (amount of involved money, ambigious) is:

 

All the money you owe to person 1 + all the money you owe to person 2 = 150 + 100 = 150

 

However, the question assumes that the formula to calculate the total amount of involved money is:

 

Part of the money you owe to person 1 + all of the money you owe to person 2 + chocolates = 70 + 20 + 20 = 140

 

The formula presented by the question is bogus.

Edited February 12, 201610 yr by Botre

boooring its friday im drunk

boooring its friday im drunk

 

Why would you drink while sitting at the computer.

Why would you drink while sitting at the computer.

 

crippling alcoholism